The patch titled
Subject: mm, compaction: keep cached migration PFNs synced for unusable pageblocks
has been added to the -mm tree. Its filename is
mm-compaction-keep-cached-migration-pfns-synced-for-unusable-pageblocks.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-keep-cached-migration-pfns-synced-for-unusable-pageblocks.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-keep-cached-migration-pfns-synced-for-unusable-pageblocks.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm, compaction: keep cached migration PFNs synced for unusable pageblocks
Migrate has separate cached PFNs for ASYNC and SYNC* migration on the
basis that some migrations will fail in ASYNC mode. However, if the
cached PFNs match at the start of scanning and pageblocks are skipped due
to having no isolation candidates, then the sync state does not matter.
This patch keeps matching cached PFNs in sync until a pageblock with
isolation candidates is found.
The actual benefit is marginal given that the sync scanner following the
async scanner will often skip a number of pageblocks but it's useless
work. Any benefit depends heavily on whether the scanners restarted
recently so overall the reduction in scan rates is a mere 2.8% which is
borderline noise.
Link: http://lkml.kernel.org/r/20190104125011.16071-18-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/compaction.c~mm-compaction-keep-cached-migration-pfns-synced-for-unusable-pageblocks
+++ a/mm/compaction.c
@@ -1967,6 +1967,7 @@ static enum compact_result compact_zone(
unsigned long end_pfn = zone_end_pfn(cc->zone);
unsigned long last_migrated_pfn;
const bool sync = cc->mode != MIGRATE_ASYNC;
+ bool update_cached;
unsigned long a, b, c;
cc->migratetype = gfpflags_to_migratetype(cc->gfp_mask);
@@ -2019,6 +2020,17 @@ static enum compact_result compact_zone(
last_migrated_pfn = 0;
+ /*
+ * Migrate has separate cached PFNs for ASYNC and SYNC* migration on
+ * the basis that some migrations will fail in ASYNC mode. However,
+ * if the cached PFNs match and pageblocks are skipped due to having
+ * no isolation candidates, then the sync state does not matter.
+ * Until a pageblock with isolation candidates is found, keep the
+ * cached PFNs in sync to avoid revisiting the same blocks.
+ */
+ update_cached = !sync &&
+ cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1];
+
trace_mm_compaction_begin(start_pfn, cc->migrate_pfn,
cc->free_pfn, end_pfn, sync);
@@ -2050,6 +2062,11 @@ static enum compact_result compact_zone(
last_migrated_pfn = 0;
goto out;
case ISOLATE_NONE:
+ if (update_cached) {
+ cc->zone->compact_cached_migrate_pfn[1] =
+ cc->zone->compact_cached_migrate_pfn[0];
+ }
+
/*
* We haven't isolated and migrated anything, but
* there might still be unflushed migrations from
@@ -2057,6 +2074,7 @@ static enum compact_result compact_zone(
*/
goto check_drain;
case ISOLATE_SUCCESS:
+ update_cached = false;
last_migrated_pfn = start_pfn;
;
}
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-do-not-wake-kswapd-with-zone-lock-held.patch
mm-compaction-shrink-compact_control.patch
mm-compaction-rearrange-compact_control.patch
mm-compaction-remove-last_migrated_pfn-from-compact_control.patch
mm-compaction-remove-unnecessary-zone-parameter-in-some-instances.patch
mm-compaction-rename-map_pages-to-split_map_pages.patch
mm-compaction-skip-pageblocks-with-reserved-pages.patch
mm-migrate-immediately-fail-migration-of-a-page-with-no-migration-handler.patch
mm-compaction-always-finish-scanning-of-a-full-pageblock.patch
mm-compaction-use-the-page-allocator-bulk-free-helper-for-lists-of-pages.patch
mm-compaction-ignore-the-fragmentation-avoidance-boost-for-isolation-and-compaction.patch
mm-compaction-use-free-lists-to-quickly-locate-a-migration-source.patch
mm-compaction-keep-migration-source-private-to-a-single-compaction-instance.patch
mm-compaction-use-free-lists-to-quickly-locate-a-migration-target.patch
mm-compaction-avoid-rescanning-the-same-pageblock-multiple-times.patch
mm-compaction-finish-pageblock-scanning-on-contention.patch
mm-compaction-check-early-for-huge-pages-encountered-by-the-migration-scanner.patch
mm-compaction-keep-cached-migration-pfns-synced-for-unusable-pageblocks.patch
mm-compaction-rework-compact_should_abort-as-compact_check_resched.patch
mm-compaction-do-not-consider-a-need-to-reschedule-as-contention.patch
mm-compaction-reduce-unnecessary-skipping-of-migration-target-scanner.patch
mm-compaction-round-robin-the-order-while-searching-the-free-lists-for-a-target.patch
mm-compaction-sample-pageblocks-for-free-pages.patch
mm-compaction-be-selective-about-what-pageblocks-to-clear-skip-hints.patch
mm-compaction-capture-a-page-under-direct-compaction.patch
mm-compaction-do-not-direct-compact-remote-memory.patch
